In a wireless communication system, a size of a geographical area where service can be provided, that is, a size of coverage of the system, is one important concern. In order to extend the coverage of the system, it is important to overcome an influence of attenuation of an electric wave used for radio communication since the electric wave is spatially attenuated due to a propagation distance, presence of an obstacle, reflection, scattering, or the like.
One technique for extending the coverage of the wireless communication system is to relay a radio signal via a relay station, that is, is relay communication. In relay communication, a relay station is located between two communication devices that are unable (or difficult) to directly transmit or receive a radio signal, and the radio signal is relayed by the relay station. For example, improving throughput in a cell edge by utilizing relay communication of the relay station in LTE (Long Term Evolution)-Advanced, which is a next generation cellular communication standard examined in 3GPP (Third Generation Partnership Project), has been proposed.
Examples of techniques related to relay communication include Patent Literatures 1 and 2 below. A technique of applying a frame aggregation technique to a relay communication technique to improve throughput in relay communication is disclosed in Patent Literature 1. Similarly, a technique of suppressing increase of a delay time and a packet error rate caused by relaying, by the relay station integrating and relaying a plurality of packets, is disclosed in Patent Literature 2.
Here, in relay communication, there are generally two types of links, i.e., a first link between a relay source node (source node) and a relay station, and a second link between the relay station and a relay destination node (destination node). The relay station receives a radio signal transmitted from the relay source node via the first link, and transmits the received radio signal to the relay destination node via the second link. In both of the techniques disclosed in Patent Literatures 1 and 2, a plurality of MAC (Media Access Control) frames or packets received via the first link is integrated into one MAC frame or packet and relayed to the second link.